The present invention relates to a production process of isobutylene polymers.
The polymerization of isobutylene is known to proceed in a manner of cationic polymerization. As a technology for conducting such a cationic polymerization, there is known the inifer process which comprises using a compound having halogens bound to tertiary carbons (e.g. 1,4-bis(xcex1-chloroisopropyl)benzene; hereinafter abbreviated as p-DCC) as a polymerization initiator in the presence of a Lewis acid catalyst (U.S. Pat. No. 4,276,394). This technology provides for free molecular weight design through modulation of the molar ratio between an initiator and a monomer and thus allows product designs according to the application use.
The problem with the inifer process is that the initiator efficiency is decreased by side reactions such as indanylation of the initiator. To cope with this problem, methods employing electron donor or the like have been proposed (Japanese Kokai Publication Hei-02-245004, Japanese Kokai Publication Hei-01-318014, Japanese Kokai Publication Hei-03-174403, Japanese Kokai Publication Hei-08-301955).
Meanwhile, for efficient production of isobutylene polymers on a commercial scale, the technology employing a reaction solvent having a dielectric constant within a certain range and the technology which comprises purifying the used solvent and reusing it are known (Japanese Kokai Publication Hei-08-53514, Japanese Kokai Publication Hei-09-071611, Japanese Kokai Publication Hei-11-255819).
Isobutylene polymers can be converted to cured products having excellent characteristics by introducing functional groups such as vinyl groups into molecular termini and curing the polymers by means of vulcanization and crosslinking. Particularly the telechelic polymers obtainable by using a bifunctional initiator such as said p-DCC are capable of forming dense networks on curing so that cured products can be provided with high strength. However, when the functional group introduction rate is low, the number of molecules having a functional group only at one terminus is increased so that many intermolecular discontinuities are produced on curing to markedly lower the strength of the cured product.
For the introduction of functional groups into the termini of isobutylene polymers, the technology using allylsilane, 1,9-decadiene or the like is known. However, according to the prior art, the reaction for introducing functional groups into the polymer termini is inhibited by indanylation of the molecular terminus, chain transfer reaction, etc., which take place during the polymerization reaction, so that it has been difficult to obtain an isobutylene polymer with a sufficiently high functional group introduction rate.
In view of the above state of the art, the present invention has for its object to produce an isobutylene polymer having excellent performance characteristics with good efficiency on a commercial scale by suppressing side reactions at the polymer growth termini during synthesis of an isobutylene polymer.
More particularly, the object of the present invention is to produce an isobutylene polymer having a carbon-carbon unsaturated bond at a terminus thereof and adapted to express high strength on curing with good efficiency on a commercial scale through inhibition of side reactions at polymer growth termini during synthesis of the isobutylene polymer and consequent improvement in the introduction rate of the carbon-carbon unsaturated bond into the polymer terminus.
The present invention, therefore, is directed to a production process of an isobutylene polymer
which comprises carrying out a cationic polymerization of a monomer component containing isobutylene in the presence of a polymerization initiator, a catalyst, an ether compound, and an electron donor.
In a preferred embodiment, the present invention is directed to a production process of an isobutylene polymer having a carbon-carbon unsaturated bond at a terminus thereof
which comprises carrying out a cationic polymerization of a monomer component containing isobutylene in the presence of a polymerization initiator, a catalyst, an ether compound, and an electron donor, and
adding a compound having the carbon-carbon unsaturated bond for introducing the carbon-carbon unsaturated bond into the polymer terminus.
The present invention is now described in detail.
In the production process according to the present invention, an isobutylene polymer is produced by carrying out a cationic polymerization of a monomer component containing isobutylene in the presence of a polymerization initiator, a catalyst, an ether compound, and an electron donor.
In the present invention, the polymerization initiator is not particularly restricted provided that it is capable of initiating a polymerization in the presence of a catalyst, but from reactivity points of view, a compound having a halogen atom bound to a tertiary carbon is preferred. The more preferred among them is a compound in which at least one of the substituents bound to the tertiary carbon is an aromatic ring. Specifically, 1,4-bis(xcex1-chloroisopropyl)benzene (hereinafter abbreviated as p-DCC) and tricumyl chloride, etc. can be mentioned.
The amount of use of the polymerization initiator may be properly selected according to the molecular weight of the polymer to be produced. Specifically, the monomer component containing isobutylene can be used in an amount of 500 to 500,000 g relative to each mole of the polymerization initiator. To produce a polymer having a molecular weight of about 10,000, for instance, it is reasonable to use 10,000 g of the monomer component containing isobutylene for each mole of the polymerization initiator.
In the present invention, various catalysts can be used according to the combination with the polymerization initiator used but, from reactivity points of view, Lewis acid catalysts are preferred. Specifically, TiCl4, AlCl3, BCl3, ZnCl2, SnCl4, ethylaluminum chloride (C2H5AlCl2), SnBr4, etc. can be mentioned. The catalyst can be used in an amount of 0.1 to 1,000 molar equivalents relative to each mole of the polymerization initiator. It can also be used in an amount of 0.0001 to 10 molar equivalents relative to each mole of the monomer component containing isobutylene.
As the ether compound in the present invention, there can be mentioned, for example, cyclic ethers such as tetrahydrofuran, trimethylene oxide, pentamethylene oxide, 1,4-dioxane, etc. and chain ethers such as diethyl ether, ethyl n-propyl ether, n-propyl ether, and so on. The ether compound not containing a cationically polymerizable carbon-carbon unsaturated bond is preferred. To maximize the effect of the invention, the ether compound is preferably an ether compound containing 2 to 20 carbon atoms, more preferably a cyclic ether containing 2 to 10 carbon atoms, still more preferably a cyclic ether containing 2 to 10 carbon atoms one oxygen atom.
The amount of use of said ether compound is preferably 0.01 to 5 moles, more preferably 0.035 to 2.3 moles, relative to each mole of the polymerization initiator, because if the amount is too small, the effect of the invention will not be expressed and if it is too large, the polymerization reaction itself will be interfered. Also, the preferred amount of use is 0.007 to 0.32 weight % relative the total amount of the reaction mixture.
Since the ether compound is added for the purpose of inhibiting side reactions at polymer growth termini, it is preferably added at a start of polymerization.
In the present invention, the monomer component containing isobutylene may be a monomer component composed exclusively of isobutylene or a monomer component containing other cationically polymerizable monomers in addition to isobutylene. In cases where the monomer component contains other monomer or monomers, isobutylene preferably accounts for not less than 50 weight %, more preferably not less than 70 weight %, still more preferably not less than 90 weight %, based on the total amount of the monomer component.
The other cationically polymerizable monomer or monomers include, for example, aliphatic olefins such as 2-butene, 2-methyl-1-butene, 3-methyl-2-butene, pentene, hexene, cyclohexene, vinylcyclohexane, 5-ethylidenenorbornene, indene, xcex2-pinene, etc.; dienes such as cyclopentadiene, dicyclopentadiene, etc.; and styrenes such as styrene, xcex1-methylsterene, p-chlorostyrene, and so on.
The amount of use of the monomer component containing isobutylene is not particularly restricted but in order to allow the polymerization reaction to proceed in a satisfactory manner, an amount of 1 to 50 weight % relative to the total amount of the reaction mixture is preferred.
In conducting the cationic polymerization according to the invention, a solvent is preferably used for allowing polymerization to proceed efficiently. The solvent is not particularly restricted insofar as the cationic polymerization can be conducted therein, and including, for example, aromatic hydrocarbon solvents, such as benzene, toluene, biphenyl, xylene, ethylbenzene, etc.; aliphatic hydrocarbon solvents, such as octane, heptane, hexane, pentane, butane, propane, ethylcyclohexane, etc.; and chlorinated hydrocarbon solvents such as dichloromethane, chloromethane, dichloroethane, chloropropane, chlorobutane, and so on. In consideration of the physical properties of the resulting polymer, it is preferable to use an aromatic hydrocarbon solvent or a mixed solvent composed of an aromatic hydrocarbon solvent and an aliphatic hydrocarbon solvent in a volume ratio of more than 10:0 to not more than 6:4.
In conducting the cationic polymerization according to the present invention, an electron donor is further used for suppressing side reactions. The electron donor includes, for example, pyridines, amines, amides, sulfoxides, and esters. Specifically, pyridine, 2-methylpyridine methylpyridine (abbreviated as picoline), trimethylamine, dimethylacetamide (abbreviated as DMAc), dimethyl sulfoxide, ethyl acetate, etc. can be mentioned. The amount of use of the electron donor is preferably lower than that of the catalyst. The preferred amount of use is 0.01 to 10 molar equivalents relative to each mole of the polymerization initiator.
In the cationic polymerization of isobutylene or the like, mere addition of the electron donor without addition of an ether compound cannot achieve the sufficient control over molecular weight distribution, suppression of side reactions at polymer growth termini, and improvement in the introduction rate of carbon-carbon unsaturated bonds into the polymer termini. Moreover, even if the amount of addition of the electron donor is increased, the above effects may not be achieved unless the ether compound is added.
Thus, in the cationic polymerization of isobutylene or the like, the combined use of said electron donor and ether compound is preferred since in this manner, the sufficient control over molecular weight distribution, suppression of side reactions at polymer growth termini, and improvement in the introduction rate of carbon-carbon unsaturated bonds into the polymer termini can be achieved and improvement in the strength of the cured product obtained therefrom can be expressed.
The cationic polymerization according to the present invention can be carried out by blending the above-mentioned respective components. The polymerization temperature is preferably within the range of xe2x88x92100 to 0xc2x0 C., more preferably within the range of xe2x88x9280 to xe2x88x9230xc2x0 C. At an excessively high temperature, the speed of polymerization tends to be retarded and side reactions such as the chain transfer reaction will be liable to take place. At an excessively low temperature, the solubility tends to be decreased to cause precipitation of the polymer in some cases.
In the production process according to the invention, the polymer growth termini can be deactivated in situ after completion of the polymerization reaction to give an isobutylene polymer having halogen atoms or the like at termini thereof.
Furthermore, a isobutylene polymer having a reactive functional group at a terminus can also be obtained by reacting, without deactivation of the polymer growth terminus, the polymer with a compound capable of introducing the reactive functional group. In this manner, functional polymers according to the application use can be obtained. As the functional groups, there can be mentioned, for example, vinyl, allyl, hydroxyl, allyl phenyl ether, and phenol groups.
The compound capable of introducing such a functional group can be used in an amount of not more than 100 molar equivalents relative to each mole of the isobutylene polymer.
Such compounds are not particularly restricted but preferably are compounds capable of introducing a carbon-carbon unsaturated bond into a polymer terminus by addition reaction or substitution reaction with a polymer growth terminus. Specifically, compounds having carbon-carbon unsaturated bonds, preferably compounds having vinyl groups can be mentioned. Particularly preferred are compounds having two or more carbon-carbon unsaturated bonds and silicon compounds having carbon-carbon unsaturated bonds. As compounds having two or more carbon-carbon unsaturated bonds, there can be mentioned, for example, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 3-methyl-1,7-octadiene, 4-methyl-1,9-decadiene, 5-methyl-1,9-decadiene, and so on. As silicon compounds having carbon-carbon unsaturated bonds, there can be mentioned allyltrimethylsilane and so on. Since carbon-carbon unsaturated bonds can be introduced into polymer termini by adding such a compound to the polymerization system, an isobutylene polymer having a carbon-carbon unsaturated bond at a terminus thereof can be produced.
The temperature at which these compounds are reacted may generally be about xe2x88x92100xc2x0 C. to room temperature.
When, in accordance with the invention, a cationic polymerization is carried out in the presence of the ether compound and, then, a compound capable of introducing a reactive functional group into the polymer is added to the reaction system, there is obtained an isobutylene polymer with a high introduction rate of the reactive functional group. Particularly when the vinyl group is introduced into the polymer terminus, a high tensile strength can be expressed on curing because of the high introduction rate of vinyl function.
The isobutylene polymer obtainable by the present invention can be used in various applications such as coating materials, architectural sealants, and sealants for electronic components by utilizing excellent characteristics such as viscoelasticity, weather resistance, and gas barrier properties, etc.
In accordance with the present invention constituted as above, side reactions at polymer growth termini during polymerization are suppressed so that isobutylene polymers having excellent characteristics can be obtained.